1. Field of the Invention
The present invention relates to a valve device, more particularly to a valve device which is intrinsically constructed with a simple configuration and permits a fluid to flow in two opposite directions at different rates without using manual operation or electric power.
2. Brief Description of the Prior Art
There has been a variety of valve constructions in the art designed for different purposes such as flowrate control, open-and-close operation, selection of flow directions or limiting of a fluid to flow in only one direction without reversal of flow. The configurations of the valves in the art may be either simple or complicated. Also, the operation or control of a valve is generally accomplished by means of manual labor or electric power.
As an example, a valve (1) commonly used in a flow passage (2) to limit a fluid to flow in only one direction and to prevent reversal of flow is shown in FIG. 1, which permits a fluid flow therethrough from the right-hand side along the direction of arrow (A) and prevents the fluid from flowing in opposite direction as directed by arrow (B).
However, in some applications, it is desired to use a valve which allows a fluid to flow reversibly with different limitations. Such is the case when a valve is employed in a cushion device of a chair wherein the cushion device which utilizes a pneumatic system is required to provide the seat of the chair with a function which allows the seat to be lowered smoothly as a person sits down thereon and to be raised immediately and automatically as the person leave the seat. In order to achieve this purpose without contributing any complexity in the configuration, purpose which can permit the fluid of the pneumatic system to flow in two opposite directions at different rates is desirable.